1. Field of the Invention
The present invention relates to a failure diagnostic processing system, more particularly to a system for performing a diagnostic search in a computer controlled apparatus, for example, an electronic controlled automatic transmission apparatus for use in automobiles.
2. Description of the Prior Art
Obviously, the present invention can be also applied to other similar apparatuses, such as computer controlled data processing or data communication systems, and the like. However, to facilitate a better understanding of the present invention, the following explanation will be made by using the electronic controlled automatic transmission apparatus as a preferred example.
Automobiles are equipped with an automatic transmission to eliminate a difficult clutch operation by automatically effecting the so-called gear changes, thus making the operation of the automobile easy even for an unskilled driver. Various apparatuses are known and used for this purpose and, recently, there is a trend toward realizing such an automatic transmission with the aid of a microcomputer, i.e., an electronic controlled automatic transmission, control is achieved through various information signals or data, such as engine speed, rotational input-shaft speed, gear position, clutch stroke, etc., and this necessitates the use of various sensors for detecting the above-mentioned information signals. Where such sensors are used, it is important to manage these through appropriate diagnostic searches, in order to maintain high reliability in the operation of the automobile.
In the prior art, the following diagnostic search method, for example, has been proposed. In this prior art method, particular memory bits are allotted, in advance, in a certain memory for each individual sensor. If a failure is detected in any one of the sensors, the corresponding memory bit allotted to that sensor is changed from, for example, "0" to "1", so that an alarm is raised indicating the occurrence of the failure with the logic "1" bit. However, the prior art method contains problems in that, first, undesired flashing of the failure indication often occurs due to a failure which is not continual but intermittent, and second, it is difficult to investigate failures which occurred in the past but are no longer present. That is, the prior art method is inherently not available for investigating a history of failures regarding each of the sensors mentioned above.